Amplifiers generally fall into different categories, depending on their performance characteristics. One such category includes high-frequency amplifiers, which are characterized by a wide bandwidth and a low open-loop gain. Another such category includes precision amplifiers, which are characterized by a narrower bandwidth but a higher open-loop gain, the latter feature making them more precise, i.e., the voltage drop across the inputs is very small when the amplifier is connected in a closed-loop configuration.
It is difficult to achieve the dual objectives of high-frequency and precise operation in a single amplifier because the very features which broaden the bandwidth of the amplifier also tend to reduce its open-loop gain. Similarly, the design criteria which increase open-loop gain tend to reduce the high-frequency response of the amplifier.
As shown in U.S. Pat. No. 5,045,805, it is known to increase open-loop gain by connecting a pair of high-frequency amplifiers in a cascade arrangement. Since the total gain is then the product of the individual gains, the precision of the amplifier pair is improved. However, such arrangements require a compensation network to maintain stability and adjustable circuitry for proper operation.